This invention relates to a triggering switch, and more particularly to an improved triggering switch by which a running DC motor in an electrical appliance can be instantly stopped without race rotation when the power source is turned off.
Electrical motors have been widely used in most electrical appliances, particularly in that type of miniaturized electrical appliances used for manual operations such as electrical drills, grinding wheels, saws, etc.. Because the structure of these manual appliances is light and portable, and the DC motor installed therein is usually reversible. To operate the DC motor, these electrical appliances are normally provided with a triggering switch in the body structure. This known triggering switch, as shown in FIG. 1, is mainly composed of a base member 1, a pressing member 2, a contact shaft 3, a number of contacting terminals 4 and a selection button 5. During manual operation, pressing down the pressure member 2 causes the contact shaft to be moved forward to connect with the contacting terminals 4, the power thereof thus being turned on to start the motor (not shown) connected therewith. When the pressure is released from the pressure member 2, the contact shaft 3 will be moved backward to disconnect the contacting terminals 4, and the power thereof is thus turned off. The rotating direction of the motor can be changed by turning the selection button 5 to one side, thus turning the contact shaft to a certain degree, and pressing the pressing member 2. The motor will then rotate in a reverse direction because the polarity of the power supply is changed along with the turning of the contact shaft 3.
Although the structure of the conventional triggering switch, as shown in FIG. 1. is simple and the operation is convenient, it still suffers a problem, i.e. when the power is turned off, the motor and the motor shaft will not stop running until after a period of race rotation. Therefore, after the pressure released from the pressing member 2, the user has to keep on holding the tool and waiting until the motor has completely stopped rotating before putting it down or returning it to its original place. This inconvenient condition wastes much time and manpower in a factory assembly line, and often causes injury to human beings and damage to other articles close to it.